Gsub and single quote issue

ruby-talk
1

a = " Ruby's gem "

puts a.gsub(/[']/, "") #=> 1. Rubys gem

puts a.gsub(/[']/, "'") #=> 2. Ruby's gem

puts a.gsub(/[']/, "\'") #=> 3. Ruby's gem

puts a.gsub(/[']/, "\\'") #=> 4. Rubys gem s gem

puts a.gsub(/[']/, "\\\'") #=> 5. Rubys gem s gem

puts a.gsub(/[']/, "\\\\'") #=> 6. Ruby\'s gem

puts " "

I couldn't understand the result for #4 and #5. Any explanation is
appreciated.

···

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Posted via http://www.ruby-forum.com/.

2

The sequence \' in a replacement string is interpreted as the post match. That's why you see the duplication. You'll see this nicely by bracketing the replacement:

irb(main):012:0> a = " Ruby's gem "
=> " Ruby's gem "
irb(main):013:0> a.gsub /'/, "<\\'>"
=> " Ruby<s gem >s gem "

There is also pre match:

irb(main):014:0> a.gsub /'/, "<\\`>"
=> " Ruby< Ruby>s gem "

Kind regards

  robert

···

On 24.03.2009 21:32, Raj Singh wrote:

a = " Ruby's gem "

puts a.gsub(/[']/, "") #=> 1. Rubys gem

puts a.gsub(/[']/, "'") #=> 2. Ruby's gem

puts a.gsub(/[']/, "\'") #=> 3. Ruby's gem

puts a.gsub(/[']/, "\\'") #=> 4. Rubys gem s gem

puts a.gsub(/[']/, "\\\'") #=> 5. Rubys gem s gem

puts a.gsub(/[']/, "\\\\'") #=> 6. Ruby\'s gem

puts " "

I couldn't understand the result for #4 and #5. Any explanation is
appreciated.

--
remember.guy do |as, often| as.you_can - without end

3

Robert Klemme wrote:

The sequence \' in a replacement string is interpreted as the post
match.

I assume that has something to do with ruby's crazy global variables,
e.g $'. In that case, why isn't the '$' required.

···

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Posted via http://www.ruby-forum.com/\.

4

The replacement string is interpreted by sub and gsub and this is just the convention that was chosen. Btw, it's the same convention as in sed and a number of other regular expression based replacement tools as well.

Kind regards

  robert

···

On 25.03.2009 06:18, 7stud -- wrote:

Robert Klemme wrote:

The sequence \' in a replacement string is interpreted as the post
match.

I assume that has something to do with ruby's crazy global variables, e.g $'. In that case, why isn't the '$' required.